A short explanation of the vagaries of the Vulcan fuel system is necessary to understand what went on on this occasion. The 1&2 tanks were in the forward fuselage and their pumps were the ones on the essential bus bar. Thus, if it all went t.. u.. that's where you wanted the bulk of your fuel. The auto refuel catered for this at part loads and the normal tank use sequence in flight also allowed for it. Thus as fuel was used the centre of gravity moved slowly forward. No problem in flight, but it was desirable to have it a bit further aft for landing in order to improve pitch control.
At the time of the incident, late 1960s, it was normal practice to switch on the fuel transfer pumps at some point late in the display to move the c of g into an optimum position for landing. Switching the pumps off was covered in the pre-landing checks. So far so good.
On the day in question, instead of taking off and going straight into the display or commencing after a shortish transit we had a long transit to perform our first display and an even longer one before the next display after which we would land. Therefore our fuel load was a higher than normal on departure.
The first display was uneventful and we duly arrived for our second show of the day in good order. The c of g was a bit further forward than usual but we had thought about this and agreed that we would turn on the transfer pumps a bit sooner than usual in the sequence. The first caution was here, we were going to do something different from normal during a display. On arrival at the hold we were informed that there was a 6 minute delay on our display time. Fine, now came the bright idea! Let's transfer some fuel now and then we can revert to normal in the display. Second caution, don't do anything you haven't thought about or practised! No sooner had we started to transfer fuel than the hold was cancelled and we were needed on stage as soon as possible.
The display went OK but something seemed slightly different about the aircraft. When it came to the point when I would normally switch on the transfer pumps I realised why. They had been on since leaving the hold and the c of g was well on its way back to Waddington all on its own. The aircraft was now getting decidedly "twitchy".
I quickly reversed the transfer pumps in an effort to retrieve the situation, but the approach was interesting and the flare at light weight even more so!. Once on the ground the nose wheel felt disturbingly light as we taxied very gingerly to our parking spot. We were still transferring fuel forward when we arrived.
What did I learn that day? Well the practice of putting on the transfer pumps during the display wasn't really that clever. It probably wouldn't be done now, but that's what we did back then. But most importantly, don't do anything in a display that you haven't thought through and thoroughly discussed beforehand and don't do anything that you haven't done in practice. Even the most innocuous things can catch you out.
YS
Last edited by Yellow Sun; 28th Jun 2017 at 21:28.